Building trusses and wall panels are composite structural components generally composed of multiple pieces of dimensional lumber (e.g., 2″×2″, 4″×2″, 4″×4″, etc.) and metal support plates (e.g., gang nails, strip gang nails, nail plates, hand nail plates, etc.). Each structural component is specifically designed to support specific loads and stresses. There are unique lumber size, lumber grade, and support plate size, placement, and orientation requirements for each design. Additionally, the lumber and support plates have placement and orientation tolerances which must be met in order to ensure that the structural component can meet its engineering and design requirements. Generally, the fabrication of a structural component is a highly automated process and a number of patents exist on inventions related to fabrication including automated design, automated lumber cutting, automated layout, and automated securing of support plates into the lumber. In fabricating a structural component, the lumber and support plates are initially laid out to form the structural component, and a set of pinch rollers are used to secure the support plates into the lumber. However, it is very common for the support plates to become dislodged or misplaced before they are pressed into place by the pinch rollers. Should such defects not be discovered before installation, the structural component may not be able to support the load and stress it was designed to support, and disastrous consequences may result.
It is therefore desirable to individually inspect each structural component prior to installation in order to confirm that the size, placement, and orientation of all elements correspond to the design specifications (i.e., that the measured size, placement, and orientation is within design tolerances). Although the structural component may be manually inspected, doing so may be impractical since a particular structural component may be quite large (e.g., approximately 15 feet wide by 60 feet long) and have support plates on both sides. Further, the number of measurements and complex calculations required to validate a structural component may consume a significant amount of time and may be prone to human error. Thus, automated and/or machine validation of fabricated construction parts is desirable.
In some conventional art, machines detect missing or grossly misplaced metal support plates by utilizing “Hall effect” sensors on one or more sides of a truss (see, e.g., U.S. Pat. No. 6,100,810 and U.S. Pat. No. 6,990,384). Such implementations can only detect gross position errors of metal parts, since the detection resolution is limited by the placement density of the sensors. Thus, these machines are generally unable to detect whether the correct support plates have been installed or whether the support plates are correctly positioned within design tolerances on the lumber pieces. And since “Hall effect” sensors are not reactive to non-metallic and non-magnetic components, conventional art machines can not validate the size, placement, and/or orientation of the lumber pieces of the truss.
To solve this deficiency, other conventional art machines have included an array of photosensors and reflectors situated such that as the truss passes through the machine, the optical connection between a photosensor and a reflector is broken (similar to a convenience store door chime) (see, e.g., U.S. Pat. No. 5,506,914). These machines are also limited to identifying only a coarse outline of the truss and the gross position errors of metal parts. The visual feedback which is provided from such a machine to an operator is restricted to a rough outline. In the continuing development of the building industry, greater accuracy, reduced tolerances and/or higher inspection standards make such machines inadequate for current structural component inspection purposes.
In other industries, optical based measurement machines have been used to measure critical dimensions with great accuracy. The use of optical measurement techniques is generally preferred over contact or magnetic techniques because of their superior resolution and thus accuracy. In addition, optical measurement techniques allow for archival and retrieval of an image of a part, if needed. In one example, defects in planar-processed wood may be detected by one or more lasers (see, e.g., U.S. Pat. No. 6,336,351). However, use of such optical based measurement techniques has not been used in the structural component fabrication industry. This is partially due to the relatively large size of typical structural components which creates significant challenges not only in the construction of suitable measurement machines and devices. It is also partially due to the difficulties in capturing, storing, and processing of large amounts of optical data.
For example, using conventional approaches, optical measurement of a truss measuring 15 feet wide by 60 feet long with an accuracy of 1/16 of an inch may require an image data on the order 4096×16384 pixels, resulting in approximately 67 megabytes (MB) of data for a simple black and white image. A sixteen bit gray scale image would result in 1070 MB of data. When in some applications it is desired to obtain images of both or even all sides of a truss, the amount of data would increase by a multiplicative factor. It may be also be desired to permanently store one or more images of a truss for reference at a later time. Even with the decreasing cost of data storage, saving one or more of such large images would quickly be cost prohibitive. In addition, such large data may not be efficiently processed in a reasonable time.
Individual parts of structural components may vary greatly with respect to the characteristics that can be measured using image processing. For example, trusses, wall frames and other structural components incorporate lumber and nail plates, among other things; and while the nail plates are generally produced according to very tight tolerances, the characteristics of the lumber (e.g., size, shape, etc.) may vary much more dramatically. It is therefore desirable to provide systems, methods and apparatus for measuring such structural components that take advantage of the regular nature of the nail plates while also dealing with the greater variation within the lumber.
With respect to building trusses, the very large potential sizes of the trusses require a large fabrication space. Often, this takes place outdoors and/or under a canopy that may only provide partial shade. Little additional space may be available for additional machines for inspecting the trusses. It is therefore desirable to provide reasonably sized machines that are capable of capturing precise and useful images of fabricated trusses for inspection purposes that can tolerate outdoor environments including, without limitation, significant swings in temperature as well as significant shifts in ambient lighting or brightness from full sun to relative darkness.
It is therefore desirable to provide systems, apparatuses, and methods which are capable of capturing, saving, and processing precise images of pre-engineered structural components, including but not limited to building trusses, wall panels, and other fabricated or composite construction parts, whereby the construction thereof may be efficiently and accurately verified.